In the past, bedding sets, also referred to as mattress sets, typically included an upper spring-core mattress formed of a resiliently compressible assemblage of helical coil springs and a lower foundation commonly referred to as a box spring also formed of a compressible spring core but substantially more firm than the mattress. Over recent years, however, as mattress designs have changed and improved, it has become more common for bedding sets to include a substantially rigid non-compressible bedding foundation, whose primary function is to provide an elevated support surface for the mattress. The present invention relates to such essentially rigid bedding foundations which, although generally not comprising any springs per se, are still commonly referred to as box springs.
A completed bedding foundation comprises several diverse components which are typically made by different manufacturers. The internal structure of a bedding foundation is substantially entirely constructed of wire components and is typically made by a first manufacturer. This wire structure may include a plurality of support modules or other support structures connected to a wire grid assembly that forms a support surface. The wire structure is mounted onto a wooden slatted base typically made by another manufacturer, often also the manufacturer of the finished foundation. The process of making the completed bedding foundation is accomplished by attaching the wire structure to the wooden slatted base, and then applying padding and a fabric cover about the core structure.
There are many different known embodiments of the wire structure used in bedding foundations, but a common characteristic of many recent designs is that the wire structure has a configuration that enables multiple wire structures to be nested with each other in a stacked assembly to enhance their compactness for shipping and storage purposes and thereby reduce the associated costs. Specifically, when one wire structure is placed atop another like wire structure, portions of the upper wire assembly fit at least partially within the lower wire assembly, whereby their assembled height is less than the sum of their individual heights. Various examples of such nestably stackable configurations are known, such as are disclosed in U.S. Pat. Nos. 5,967,499, and 5,052,064.